In leu[sic] of a formal language specification our goal is simple, and we’re very close.
Relying on bugs is no different to relying on an undocumented API and violates your contract with us.

These two policies might be reasonable in isolation, but the combination is entirely unreasonable. Without an actual spec, there is no way to tell the difference between a bug and a feature. Users cannot be reasonably expected to test all their inputs against a different tool in a whole different language.